Corn Response to Nitrogen Source, Drainage, and Irrigation in a Claypan Soil.

This 2006 and 2007 study of corn (Zea mays L.) evaluated the effects of nitrogen (N) sources [non-treated control, anhydrous ammonia, urea, polymer-coated urea (PCU), and 32% urea ammonium nitrate (UAN) at 168 kg N ha^-1] and water management systems [drained, non-irrigated (DNI) at 6.1, 9.2, and 12.2 m spacings; non-drained, non-irrigated (NDNI); non-drained, overhead irrigated (NDOHI); and drained plus subirrigated (DSI) at 6.1, 9.2, and 12.2 m spacings] on yield, plant population, grain protein, and grain N removal. DNI increased grain yield 0.92 to 1.88 Mg ha^-1 (10% to 22%) compared to NDNI. DSI increased yields up to 4.41 Mg ha^-1 (24% to 38%) depending on N source and spacing. Nitrogen sources in the NDOHI increased yields 42% to 45% compared to NDNI, and 10% to 20% compared to DSI 6. In irrigated and poorly drained claypan soil (NDOHI), PCU increased yield 0.88 Mg ha^-1 compared to NCU. PCU had the highest yields among N sources with DSI 6, DSI 9, DSI 12, and DNI 12. In a well drained soil (DNI 6), NCU had the highest yield (8.94 Mg ha^-1) among N sources, while anhydrous ammonia had the highest yields in the NDNI control (7.89 Mg ha^-1) and DNI 9 (9.07 Mg ha^-1). Grain N removal was greatest (201.9 to 202.2 kg ha^-1) with anhydrous ammonia and PCU with NDOHI. Nitrogen source selection is an important component of high-yielding corn production systems depending on water management system.